Routing is a process of transmitting information from the source to the destination through a network. Routing generally includes two basic actions: determining the best path, and exchanging data. Metric is a metric criterion (such as path length) for determining the best path to the destination in a routing algorithm. To help select the path, the routing algorithm initializes and maintains the routing table that includes path information. The path information varies with the applied routing algorithm. The best mode of telling a router about the destination address or the next-hop address is to send a packet to the router that represents the “next hop”. When receiving the packet, the router checks the destination address of the packet, and attempts to correlate this address with the “next hop”. A routing table includes multiple types of information such as distance information, hop count, and “next hop” address. The Metric varies with the applied routing algorithm. The routing table compares the Metric to determine the best path. In this way, the routers communicate with each other, and maintain their routing table by exchanging routing information. Route update information generally includes all or partial routing tables. By analyzing the route update information from other routers, a router sets up a network topological view. Another example of sending information between routers is to send link state advertisement information; the router informs other routers of the router's link state, where the other routers have sent the link state advertisement information. The link state advertisement information is used to set up a complete topological view and enable the router to determine the best path.
Multi-homing means that a link group of more than one link (belonging to the same service provider or different service providers) is set up between an end user and a network for the purpose of connection survivability or load balancing. Traffic engineering is a set of tools and methods for retrieving the best service from a given infrastructure no matter whether the network device and the transmission line are normal or not. Traffic engineering involves optimization of the installed resources. With extensive deployment of multi-homing networks and traffic engineering, Internet routes increase rapidly. The capacity of a Forwarding Information Base (FIB) is limited, and a routing table storage chip of greater capacity is required.